[In vitro comparison of the shear bond strength of "etch and rinse" vs "self-etch" bonding systems on dentin after "nonvital tooth bleaching"]

ABSTRACT

Since bleaching causes changes on dental tissue and affects adhesive bond strengths, it is useful to recognize bonding systems which provide higher bond strengths on the dentin after bleaching. Forty eight human sound premolars were selected and sectioned 5mm below the CEJ. In order to do the bleaching process, the access cavity preparation was done and after the excavation of pulp tissue, and placement of the hybrid glass ionomer base at the apex, the teeth were bleached using the 35% hydrogen peroxide for 4 times. The teeth were then embedded in a self-cured acrylic resin and polished to obtain a flat dentin surface. The teeth were assigned into 4 groups according to the adhesive system used [n=12] group 1 Single Bond [SB], group 2 Prime and Bond NT [P and B], group 3 Clearfil SE Bond [CSE] and group 4 Opti Bond [All in one] [OB]. The adhesive systems were used according to the manufacturer's instructions and a cylinder of composite resin Z100 was overlied. The teeth were thermocycled and the shear bond strength tests were performed in a universal testing machine with cross head speed of 1mm/min. CSE had the highest bond strength [15.18 MPa] and SB had the lowest one [8.10 MPa]. One Way ANOVA and independent sample t-test showed that the difference in bond strength values among the different types or generations of bondings was statistically significant except for the SB and P and B systems [P<0.05]. Within the limitations of this study, it is concluded that two step "self-etch" adhesives [CSE] are preferred to use for the teeth undergoing "Non vital tooth bleaching" with 35% hydrogen peroxide than the one step "self-etch" adhesives [OB] or two step "etch and rinse" adhesives [SB, P and B]